Possible role of liver cytosolic and mitochondrial aldehyde dehydrogenases in acetaldehyde metabolism
Possible role of liver cytosolic and mitochondrial aldehyde dehydrogenases in acetaldehyde metabolism
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DOI：
10.1021/bi9521093
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发表时间：
1996-04-09
期刊：
影响因子：
2.9
通讯作者：
Keung, WM
中科院分区：
文献类型：
--
作者：
Klyosov, AA;Rashkovetsky, LG;Keung, WM
为了解实验动物中抗干渴剂的可能作用机制提供分子基础，从仓鼠和大鼠肝脏中纯化并鉴定了醛脱氢酶（ALDH）同工酶，并与人的ALDH同工酶进行了比较。这些物种的线粒体ALDH在氧化和水解反应中表现出几乎相同的动力学性质。然而，人源的胞质ALDH与啮齿类动物的胞质ALDH显著不同。因此，对于人ALDH-1，乙醛的Km值为180 +/-10 μ M，而仓鼠ALDH-1和大鼠ALDH-1的Km值分别为12 +/-3和15 +/-3 μ M。在pH 9.5下测定的K-m值与在pH 7.5下测定的K-m值几乎相同。在体外，人ALDH-1对双硫仑抑制的敏感性比仓鼠和大鼠胞质ALDH低10倍。乙醛和芳香醛或萘醛之间的竞争ALDHs的结合和催化位点表明，它们的地形是复杂的一个以上的结合位点。这也来自底物抑制和活化、NAD（+）对ALDH催化的对硝基苯基酯水解的影响、对醛和对硝基苯基酯的底物特异性以及双硫仑对ALDH催化的氧化和水解的抑制的数据。数据进一步表明，乙醛不能被认为是针对芳香族ALDH底物（例如生物醛）的研究的“标准"ALDH底物。显然，在人类肝脏中，只有线粒体ALDH在生理浓度下氧化乙醛，而在仓鼠或大鼠肝脏中，线粒体和细胞溶质同工酶都将这样做。
TO provide a molecular basis for understanding the possible mechanism of action of antidipsotropic agents in laboratory animals, aldehyde dehydrogenase (ALDH) isozymes were purified and characterized from the livers of hamsters and rats and compared with those from humans. The mitochondrial ALDHs from these species exhibit virtually identical kinetic properties in the oxidation and hydrolysis reactions. However, the cytosolic ALDH of human origin differs significantly from those of the rodents. Thus, for human ALDH-1, the K-m value for acetaldehyde is 180 +/- 10 mu M, whereas those for hamster ALDH-1 and rat ALDH-1 are 12 +/- 3 and 15 +/- 3 mu M, respectively. K-m values determined at pH 9.5 are virtually identical to those measured at pH 7.5. In vitro human ALDH-1 is 10 times less sensitive to disulfiram inhibition than are the hamster and rat cytosolic ALDHs. Competition between acetaldehyde and aromatic aldehydes or naphthaldehydes for the binding and catalytic sites of ALDHs shows their topography to be complex with more than one binding site. This also follows from data on substrate inhibition and activation, effects of NAD(+) on ALDH-catalyzed hydrolysis of p-nitrophenyl esters, substrate specificity toward aldehydes and p-nitrophenyl esters, and inhibition by disulfiram in relation to oxidation and hydrolysis catalyzed by the ALDHs. The data further suggest that acetaldehyde cannot be considered as a ''standard'' ALDH substrate for studies aimed at aromatic ALDH substrates, e.g. biogenic aldehydes. Apparently, in human liver, only mitochondrial ALDH oxidizes acetaldehyde at physiological concentrations, whereas in hamster or rat liver, both the mitochondrial and cytosolic isozymes will do so.